The present invention relates to improvements in line securing devices known as cam cleats, which are widely used to secure line on sailing craft due to the ability of such devices to carry high loads and to quickly secure and release a line. The device includes a pair of facing pawls that are rotatably mounted on a shaft and spring loaded in opposite rotary directions, whereby the pawls are urged toward each other in a closed position. The facing surfaces of the pawls bear teeth, and said surfaces have a gradually decreasing radius from the shaft such that the distance between pawls is increased when rotated from a closed to an open position. Thus, a line inserted between the pawls may be pulled between the teeth in the open direction, but the pawls close to grip or clamp the line when pull is exerted in the opposite direction, in effect providing a unidirectional self-locking mechanism. The line is quickly released from engagement between the pawls by a quick pull away from the pawls and is quickly engaged by pulling of the line between the pawls.
In prior art cam cleats the cams or pawls have been swingably mounted on a vertical cylindrical shaft extending upward from a base. The cams each include a vertical cylindrical bore to receive the shaft, whereby the cam is journaled on the shaft in the manner of a sleeve bearing.
If the cam cleat is to be used on a wide variety of sail craft, the cleat must be able to accommodate a variety of line diameter. In addition, the cleat must be operative to accommodate both light and heavy loads.
There are several disadvantages in the use of a conventional cam cleat when variable loads are placed on the line. Heretofore, very strong or high tension springs have been used to rotate the cam toward a closed position to overcome the friction between the cam and its shaft, thereby to prevent slipping of the line toward the loaded direction or to prevent accidential release. The use of such heavy springs resists opening of the pawls and increases the effort required to engage the line. Under high loads, considerable lateral forces are exerted from the line to the sleeve bearing surfaces of the cam and shaft, greatly increasing rotational friction and making it difficult to disengage the line from a locked position. The necessity to accommodate high loads also requires the use of springs which are sufficiently heavy to overcome the increased friction, whereby the pawls will continue the grip the line.
Another inherent drawback of prior art cam cleats is the necessity to use pointed teeth having a radius of less than 0.01 inches on the line engaging surfaces of the pawls. Under heavy loads, a situation may be encountered where the rotary friction on the pawl exceeds the spring force utilized to urge the pawl toward a closed position. At this stage, the line, which has been squeezed to a reduced diameter, would tend to slip. For this reason, sharp teeth have to be utilized to create additional friction against slipping. The pointed teeth tend to abraid or shred the line under heavy loads and many cam cleats therefore have the reputation of being "line eaters."